---
title: Using Bun
description: A guide on using Bun with Expo and EAS.
---

import { Terminal } from '~/ui/components/Snippet';

[Bun](https://bun.sh/) is a JavaScript runtime and a drop-in alternative for [Node.js](https://nodejs.org/en). In Expo projects, Bun can be used to install npm packages and run Node.js scripts. The benefits of using Bun are faster package installation than npm, pnpm, or Yarn and [at least 4x faster startup time compared to Node.js](https://bun.sh/docs#design-goals), which gives a huge boost to your local development experience.

## Prerequisites

> **Note:** While Bun replaces Node.js for most use cases in your project, at this time, a [Node.js LTS version](https://nodejs.org/) is still required to be installed for the `bun create expo` and `bun expo prebuild` commands. These commands use `npm pack` to download project templates.

To create a new app using Bun, [install Bun on your local machine](https://bun.sh/docs/installation#installing).

## Start a new Expo project with Bun

To create a new project, run the command:

<Terminal cmd={['$ bun create expo-app my-app']} />

You can also run any **package.json** script with `bun run`:

<Terminal cmd={['$ bun run ios']} />

To install any Expo library, you can use `bun expo install`:

<Terminal cmd={['$ bun expo install expo-audio']} />

## Use Bun for EAS builds

EAS decides which package manager to use based on the lockfile in your codebase. If you want EAS to use Bun, run `bun install` in your codebase which will create a **bun.lockb** (the Bun lockfile). As long as this lockfile is in your codebase, Bun will be used as the package manager for your builds. Make sure to delete any lockfiles generated by other package managers.

### Customize Bun version on EAS

Bun is installed by default when using EAS. See the [Android server images](/build-reference/infrastructure/#android-server-images) and [iOS server images](/build-reference/infrastructure/#ios-server-images) to learn which version of Bun is used by your build's image.

To use an [exact version of Bun](/eas/json/#bun) with EAS, add the version number in **eas.json** under the build profile's configuration. For example, the configuration below specifies Bun version `1.0.0` for the `development` build profile:

{/* prettier-ignore */}
```json eas.json
{
  "build": {
    "development": {
      /* @info Use <CODE>bun</CODE> property in eas.json to specify the exact version.*/
      "bun": "1.0.0"
      /* @end */
      /* @hide ... */ /* @end */
    }
    /* @hide ... */ /* @end */
  }
}
```

## Trusted dependencies

Unlike other package managers, Bun does not automatically execute lifecycle scripts from installed libraries, as this is considered a security risk. However, if a package you are installing has a `postinstall` script that you want to run, you have to explicitly state that by including that library in your [`trustedDependencies`](https://bun.sh/guides/install/trusted) array in your **package.json**.

For example, if you install `packageA`, which has a dependency on `packageB` and `packageB` has a `postinstall` script, you must add `packageB` in your `trustedDependencies`.

To add a trusted dependency in your **package.json**, add:

```json package.json
"trustedDependencies": ["your-dependency"]
```

Then, remove your lockfile and re-install the dependencies:

<Terminal
  cmd={['$ rm -rf node_modules', '$ rm bun.lockb', '$ bun install']}
  cmdCopy="rm -rf node_modules && rm bun.lockb && bun install"
/>

## Common errors

### EAS Build fails when using Sentry and Bun

If you're using `sentry-expo` or `@sentry/react-native`, these depend on `@sentry/cli`, which updates source maps to Sentry during your build. The `@sentry/cli` package has a `postinstall` script which needs to run for the "upload source maps" script to become available.

To fix this, add `@sentry/cli` to your [trusted dependencies](/#trusted-dependencies) array in **package.json**:

```json package.json
"trustedDependencies": ["@sentry/cli"]
```
